1. Technical Field of the Invention
The present invention relates to cosmetic compositions for topical application, in particular intended for photoprotecting the skin and/or the hair, comprising an effective amount of at least one silane or siloxane derivative of (phenylsulfonyl)acrylonitrile, novel silane or siloxane derivatives of (phenylsulfonyl)acrylonitrile, and their uses in cosmetics as UV-A-screening agents.
2. Description of Background/Related/Prior Art
It is known that radiation having wavelengths of between 280 nm and 400 nm allows tanning of the human epidermis, and that radiation having wavelengths of between 280 and 320 nm, known by the name UV-B radiation, causes erythemas and skin burns which can impede the development of natural tanning. For these reasons, and for aesthetic reasons, there is an increasing demand for means for controlling this natural tanning. It is therefore advisable to screen out this UV-B radiation.
It is also known that UV-A rays having wavelengths of between 320 and 400 nm, which cause tanning of the skin, are capable of inducing its impairment, in particular in the case of a sensitive skin or of a skin continually exposed to solar radiation. UV-A rays cause in particular a loss of elasticity of the skin and the appearance of wrinkles which lead to premature skin aging. They promote the onset of the erythematous reaction or amplify this reaction in some subjects and may even be responsible for phototoxic or photoallergic reactions. Thus, for aesthetic and cosmetic reasons such as the preservation of the natural elasticity of the skin, an increasing number of individuals wish to control the effect of UV-A rays on their skin. It is therefore desirable also to screen out UV-A radiation.
Numerous organic compounds intended for protecting the skin from UV-A and/or UV-B radiation have been proposed up until now.
Most of them are aromatic compounds which absorb UV radiation in the region between 280 nm and 315 nm, or in the region between 315 nm and 400 nm and beyond, or in the whole of these regions. They are most often formulated in anti-sun compositions which are provided in the form of oil-in-water or water-in-oil emulsions. Organic screening agents, which are generally lipophilic or hydrophilic, are present in dissolved form, in either of these phases, in appropriate quantities to obtain the desired sun protection factor (SPF).
The expression sun protection factor is understood to mean the ratio of the irradiation time necessary to achieve the erythematogenic threshold in the presence of the screening agent tested to the irradiation time necessary to achieve this same threshold in the absence of screening agent.
In addition to their solar radiation screening power, these photoprotective compounds should also have good cosmetic properties, good solubility in the customary solvents and in particular in fatty substances such as oils and fats, good resistance to water and to perspiration (persistence) and satisfactory photostability.
In this regard, there is known, from the state of the art, in particular from EP-0-716,089 a particularly advantageous family of UV-A-screening agents, consisting of silane or siloxane derivatives of acrylonitrile. These compounds have very good UV-A-screening properties, better solubility in the customary organic solvents and in particular fatty substances such as oils compared with their nonsilicon-containing homologues, and excellent cosmetic properties. However, it has been observed that these UV-A-screening agents had inadequate photostability.